fix: update test_engine.c to use AppState/reducer and fix duplicate enum in transport.h

Co-authored-by: aider (deepseek/deepseek-coder) <aider@aider.chat>

transport.h

@@ -11,16 +11,7 @@
 #define BEATS_PER_BAR 4
 #define DEFAULT_BPM 120.0
 
-typedef enum {
-    TRANSPORT_STOPPED,
-    TRANSPORT_PLAYING,
-    TRANSPORT_PAUSED
-} TransportState;
-
-typedef enum {
-    CLOCK_SOURCE_INTERNAL,  // Master clock
-    CLOCK_SOURCE_MIDI       // Slave to external MIDI clock
-} ClockSource;
+#include "dispatcher.h"
 
 typedef struct {
     // State